1. Technical Field
The present invention relates in general to RFID technology, and in particular to a method and system for using RFID technology to locate devices. Still more particularly, the present invention relates to a method and system for cost-effectively locating devices using RFID technology.
2. Description of the Related Art
The use of radio frequency (RF) identification (RFID) technology to locate devices that are equipped with an RFID tag (i.e., an electronic tag that emits an RFID signal when triggered by an RF signal) is generally known in the art. In conventional systems, a number of RF transceivers are provided in a monitored environment. These transceivers generate and transmit RF signals in a particular sub-area defined by the strength of the RF signal and location of the RF transceiver relative to the area of projection.
Thus, in a retailed environment, for example, the RF transceivers may be placed in the ceiling of the retail environment, and the area of projection is some diameter immediately below the RF transceiver. The transceivers are placed at a measured distance apart from each other with enough signal strength to reach the edge of the signal from an adjacent RF transceiver.
The transmitted RF signals are received by RF devices designed to respond to receipt of the RF signal by transmitting/broadcasting an identification signal in return. A typical RF device is the RFID tag, which is a low-logic (and passive) electronic component that transmits a signal containing a stored ID of the tag whenever an RF interrogation signal is sensed by the tag. When an RF interrogation signal is received by the RFID tag, a coil within the tag is energized and causes an internal chip to rebroadcast the tag's ID, which is received by the interrogating device (e.g., RF transceiver).
Typical RFID tags are omni-directional or wide viewing angle devices that do not lend themselves to receiving or producing directional signals. Because of this limitation, locating the particular RFID tag requires utilization of multiple RF interrogation devices. In this and other RF location sensing applications, readings of RF signal strength from multiple interrogating RF devices are utilized to triangulate the position of an RFID tag (or other RF device). This process often yields errors due to attenuation of RFID signal strength, etc.
In order to perform the device locating service over a large area, a large number of interrogating devices are required to continually triangulate the position of a tag, which is moved around in the area. Additionally, a background computing device must be connected to these interrogating devices to complete the triangulation calculations. Use of such a large number of high-logic (active) devices tends to be rather costly. Each high logic device is substantially more expensive to obtain than the low-logic tags. Also additional expense is incurred because each interrogating device must be powered and a central processing system that performs the triangulation calculations must be provided. Also, the triangulation method is inherently inaccurate because signal strength of the tag received by respective devices varies due to attenuation and other factors.
The substantial cost in implementing the above described device locating system by using a large number of high-logic devices limits the ability to implement the system on a large scale. Additionally, with current methods, there is no way to inform the user of the user's location relative to the RFID sensors, absent a feedback to the user of the results of the triangulation. The present invention provides a generally applicable solution to overcome these and other limitations found with the above described system.